package gu.sql2java.parser;

import net.sf.jsqlparser.expression.BinaryExpression;
import net.sf.jsqlparser.expression.Expression;
import net.sf.jsqlparser.expression.Function;
import net.sf.jsqlparser.expression.operators.conditional.AndExpression;
import net.sf.jsqlparser.expression.operators.conditional.OrExpression;
import net.sf.jsqlparser.expression.operators.relational.ComparisonOperator;
import net.sf.jsqlparser.schema.Column;
import net.sf.jsqlparser.statement.select.Join;
import net.sf.jsqlparser.statement.select.OrderByElement;
import net.sf.jsqlparser.statement.select.PlainSelect;
import net.sf.jsqlparser.statement.select.SelectItem;
import net.sf.jsqlparser.statement.select.SubSelect;
import net.sf.jsqlparser.statement.select.WithItem;
import net.sf.jsqlparser.util.TablesNamesFinder;

/**
 * 基于SQL语法对象的SQL注入攻击分析实现
 * @author guyadong
 *
 */
public class InjectionSyntaxObjectAnalyzer  extends TablesNamesFinder{
	private static final String DANGROUS_FUNCTIONS = "(sleep|benchmark|extractvalue|updatexml|ST_LatFromGeoHash|ST_LongFromGeoHash|GTID_SUBSET|GTID_SUBTRACT|floor|ST_Pointfromgeohash"
			+ "|geometrycollection|multipoint|polygon|multipolygon|linestring|multilinestring)";
	
	private static ThreadLocal<Boolean> disableSubselect = new ThreadLocal<Boolean>(){
        @Override
        protected Boolean initialValue() {
            return true;
        }};
	private ConstAnalyzer constAnalyzer = new ConstAnalyzer();
    public InjectionSyntaxObjectAnalyzer() {
		super();
		init(true);
		
	}
	@Override
    public void visitBinaryExpression(BinaryExpression binaryExpression) {
	    if(binaryExpression instanceof ComparisonOperator){
	        if(isConst(binaryExpression.getLeftExpression()) && isConst(binaryExpression.getRightExpression())){
	            throw new InjectionAttackException("DISABLE IDENTICAL EQUATION " + binaryExpression);
	        }
	    }
	    super.visitBinaryExpression(binaryExpression);
    }

    @Override
    public void visit(AndExpression andExpression) {
        super.visit(andExpression);
        checkConstExpress(andExpression.getLeftExpression());
        checkConstExpress(andExpression.getRightExpression());
    }
    @Override
    public void visit(OrExpression orExpression) {
        super.visit(orExpression);
        checkConstExpress(orExpression.getLeftExpression());
        checkConstExpress(orExpression.getRightExpression());
    }
    @Override
    public void visit(Function function) {
    	if(function.getName().matches(DANGROUS_FUNCTIONS)){
    		throw new InjectionAttackException("DANGROUS FUNCTION: "+function.getName());
    	}
    	super.visit(function);
    }
    @Override
    public void visit(WithItem withItem) {
        try {
            /** 允许 WITH 语句中的子查询 */
            disableSubselect.set(false);
            super.visit(withItem);
        } finally {
            disableSubselect.set(true);
        }
    }
    @Override
    public void visit(SubSelect subSelect) {
        if(disableSubselect.get()){
            throw new InjectionAttackException("DISABLE subselect " + subSelect);
        }
    }
    @Override
    public void visit(Column tableColumn) {
        if(ParserSupport.isBoolean(tableColumn)){
            throw new InjectionAttackException("DISABLE CONST BOOL " + tableColumn);
        }
        super.visit(tableColumn);
    }
    @Override
    public void visit(PlainSelect plainSelect) {
        if (plainSelect.getSelectItems() != null) {
            for (SelectItem item : plainSelect.getSelectItems()) {
                item.accept(this);
            }
        }

        if (plainSelect.getFromItem() != null) {
            plainSelect.getFromItem().accept(this);
        }

        if (plainSelect.getJoins() != null) {
            for (Join join : plainSelect.getJoins()) {
                join.getRightItem().accept(this);
                for(Expression e:join.getOnExpressions()){
                    e.accept(this);
                }
            }
        }
        if (plainSelect.getWhere() != null) {
            plainSelect.getWhere().accept(this);
            checkConstExpress(plainSelect.getWhere());
        }

        if (plainSelect.getHaving() != null) {
            plainSelect.getHaving().accept(this);
        }

        if (plainSelect.getOracleHierarchical() != null) {
            plainSelect.getOracleHierarchical().accept(this);
        }
        if(plainSelect.getOrderByElements() != null){
            for( OrderByElement orderByElement : plainSelect.getOrderByElements()){
                orderByElement.getExpression().accept(this);
            }
        }
        if(plainSelect.getGroupBy() != null){
            for(Expression expression : plainSelect.getGroupBy().getGroupByExpressionList().getExpressions()){
                expression.accept(this);
            }
        }
    }

    private boolean isConst(Expression expression){
        return constAnalyzer.isConstExpression(expression);
    }
    private void checkConstExpress(Expression expression){
        if(constAnalyzer.isConstExpression(expression)){
            throw new InjectionAttackException("DISABLE CONST EXPRESSION " + expression);
        }
    }
}
